This 30-Million-Year-Old Cave in New Zealand Shows an Amazing Natural Phenomenon

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Deep underground
in New Zealand's North Island, a winding underground universe of limestone
caves glow with a magical blue-green light. While it might seem like pure
fantasy, these caves are very real. Their dark interior is brought to life by
twinkling colonies of glow worms, or arachnocampa luminosa.

Auckland
photographer Joseph Michael documented the sparkling caves by spending countless
hours in the frigid underworld of the caves, which experts estimate dates back
some 30 million years.

Glow worms are the
larvae of the fungus gnat, a type of fly that resembles a mosquito.

The glow worms are
found only in New Zealand and eastern Australia. The Australian worms have
smaller lights and tend to stay in smaller groups.

The first part of
the species' name, arachnocampa, means "spider worm", and refers to
the web of silk threads the worms use to snatch their prey.

The roofs of caves
make great homes for the larvae, which often reside side-by-side in groups of
hundreds, because of their damp, sheltered surface.

The worms' glowing
light helps them attract their food - other insects.

Many other animals
are also bioluminescent, meaning they make light. The trait, which can be used
to fend off predators, snatch prey, and lure mates is so useful that it's
evolved independently at least 40 times.

Most
bioluminescent creatures live in the ocean, where their glimmers are often the
sole source of light.

If light makes its
way into the cave, the glow worms are rendered invisible to the human eye.

The insects are
active at night. Many observers have described the experience of visiting the
glow worms at night as similar to being under the stars on a clear night.

If the insects
feel interrupted, they can switch off their bioluminescence. In the presence of
torchlight, smoke, or insect repellent, for example, they have been known to
temporarily go dark, typically for as long as 15 minutes at a time.

The glow worms'
beauty is fleeting: They live just long enough to mate and lay eggs.

The eggs hatch
into larvae and then pupate into adult flies. Glow worms spend most of their
life as larvae, however: between 6 and 12 months, depending on how much food is
available.

The larvae are
entirely soft except the head capsule, and when they outgrow this portion of
their shell they moult, shedding their skin. This happens repeatedly during
their life-cycle.

At the end of the
larva stage, the insect turns into a pupa and hangs from the cave roof on a
short thread for about 1-2 weeks, glowing intermittently. While the male pupae
get progressively dimmer, the female pupae get progressively brighter.

Adult glow worms
don't fly well. As a result, they often stick to the same geological area,
building colonies. Female glow worms
lay roughly 130 eggs and die soon afterwards. About three weeks later, the eggs
hatch and the cycle repeats.